This application is based on Japanese Patent Application No. 2001-84899, the content of which is incorporated herein by reference.
The present invention relates to a rewritable display sheet for rewritably displaying an image by utilizing, for example, an electrophoretic phenomenon.
Conventionally, image display devices utilizing the electrophoretic phenomena are disclosed in, for example, Japanese Patent Laid-Open Publication Nos. HEI 10-62824, HEI 10-90732 and HEI 10-149118.
However, the image display devices disclosed in these documents and the other well-known electrophoretic display devices all display an image only on one surface, and there has existed no electrophoretic display device that can display different images on both surfaces.
Accordingly, the object of the present invention is to provide a rewritable display sheet capable of displaying images on both surfaces, an image forming apparatus for writing images on the rewritable display sheet, and an image displaying method for displaying images on the rewritable display sheet.
In order to achieve the aforementioned object, the rewritable display sheet of the present invention is provided with a conductive substrate having a voltage applying section at an end portion,
a first display layer, which is provided on a first surface of the conductive substrate and able to display a first image with a first electric field applied thereto,
a first transparent sheet provided on the first display layer,
a second display layer, which is provided on a second surface of the conductive substrate and able to display a second image with a second electric field applied thereto, and
a second transparent sheet provided on the second display layer.
Moreover, an image forming apparatus of the present invention is provided with an image writing member provided so as to be able to come in contact with the surface of the first transparent sheet of the rewritable display sheet, and a voltage applying member provided so as to be able to come in contact with the voltage applying section of the rewritable display sheet.
Moreover, an image displaying method of the present invention includes the step of, in a state in which a first voltage is applied to a voltage applying section of the rewritable display sheet, applying a second voltage to the surface of the first transparent sheet according to an image signal, whereby an image is displayed on the first display layer.
In the rewritable display sheet of the present invention, the image writing is performed in a state in which a first voltage is applied to the voltage applying section of the conductive substrate. The image writing is performed by putting an electrode to which a second voltage is applied in contact with or close to the surface of the first transparent sheet according to, for example, an image signal. When the second voltage is applied to the above-mentioned electrode, an electric field is formed between the conductive substrate and the electrode due to a potential difference between the first voltage and the second voltage. Therefore, an image is written into the first display layer by the effect of this electric field, and consequently, the image is displayed on one surface of the rewritable display sheet.
Also, when an image is written into the other surface of the rewritable display sheet on the one surface of which the image has been displayed as described above, an image is written into the second display layer by putting an electrode to which the third voltage, which may be identical with the second voltage, is applied in contact with or close to the surface of the second transparent sheet according to, for example, an image signal to form an electric field between the conductive substrate and the electrode in a state in which the first voltage is applied to the conductive substrate via the voltage applying section. In this case, if a member of the same potential as that of the conductive substrate is put in contact with the surface on which the image has already been displayed, i.e., the entire surface or part of the first transparent sheet when the image is written into the second display layer of the rewritable display sheet, then no electric field is formed between the conductive substrate and the above-mentioned member. As a result, the image written in the first display layer is not disordered but kept intact.
As described above, according to the rewritable display sheet of the present invention, different images can be displayed on both surfaces.